Method to reduce condensation in cooling zone cooler of continuous catalyst regeneration system

ABSTRACT

Systems and processes for providing a blended cooling air stream to a cooling zone cooler in a continuous catalyst regeneration system are provided that include removing a first effluent stream from a regeneration tower, providing the first effluent stream to a regeneration cooler; providing a first air stream to the regeneration cooler to form a heated first air stream, combining at least a portion of the heated first air stream with a second air stream to form a blended cooling air stream, and providing the blended cooling air stream to a cooling zone cooler.

CROSS-REFERENCE TO RELATED APPLICATION

This application is a Division of copending application Ser. No.12/342,790 filed Dec. 23, 2008, the contents of which are herebyincorporated by reference in its entirety.

FIELD OF THE INVENTION

The systems and processes disclosed herein relate to the regeneration ofspent catalyst in the art of catalytic conversion of hydrocarbons touseful hydrocarbon products, and more particularly to reducing oreliminating condensation in a cooling zone cooler utilized in acontinuous catalyst regeneration (CCR) process.

DESCRIPTION OF RELATED ART

The catalysts used in catalytic processes for the conversion ofhydrocarbons tend to become deactivated for one or more reasons. Ininstances where the accumulation of coke deposits causes thedeactivation, regenerating of the catalyst to remove coke deposits canrestore the activity of the catalyst. Coke is normally removed fromcatalyst by contact of the coke-containing catalyst at high temperaturewith an oxygen-containing gas to combust and remove the coke in aregeneration process. These processes can be carried out in-situ, or thecatalyst may be removed from a reactor in which the hydrocarbonconversion takes place and transported to a separate regeneration zonefor coke removal. Various arrangements for continuously orsemicontinuously removing catalyst particles from a reaction zone andfor coke removal in a regeneration zone have been developed.

SUMMARY OF THE INVENTION

The systems and processes disclosed herein relate to continuous catalystregeneration, particularly to such systems and processes that utilize acooling zone cooler.

In one aspect, a method of providing a blended cooling air stream to acooling zone cooler in a continuous catalyst regeneration system isprovided that includes removing a first effluent stream from aregeneration tower, providing the first effluent stream to aregeneration cooler; providing a first air stream to the regenerationcooler to form a heated first air stream, combining at least a portionof the heated first air stream with a second air stream to form ablended cooling air stream, and providing the blended cooling air streamto a cooling zone cooler. The method can also include removing a firstgas stream from a regeneration tower, passing the first gas stream to anair heater to form a heated first gas stream, dividing the heated firstgas stream to form a regeneration tower return stream and a cooling loopstream, providing the cooling loop stream to the cooling zone cooler,and cooling the cooling loop stream with the blended cooling air stream.

In another aspect, a system for continuous catalyst regeneration isprovided that includes a regeneration tower, a regeneration cooler thatreceives a first effluent stream that is removed from the regenerationtower, a cooler blower that provides a first air stream that is passedto the regeneration cooler to form a heated first air stream and asecond air stream that is combined with the heated first air stream toform a blended cooling air stream, and a cooling zone cooler thatreceives the blended cooling air stream.

BRIEF DESCRIPTION OF THE DRAWINGS

Specific examples have been chosen for purposes of illustration anddescription, and are shown in the accompanying drawings, forming a partof the specification.

FIGS. 1 and 1A are simplified flow diagrams of embodiments of acontinuous catalyst regeneration process.

FIGS. 2 and 2A are simplified flow diagrams of the air loop of thecontinuous catalyst regeneration process of FIGS. 1 and 1A.

DETAILED DESCRIPTION

FIG. 1 is a simplified flow diagram of a continuous catalystregeneration (CCR) system indicated generally at 100. As illustrated,spent catalyst 102 is removed from a reactor and is provided to acatalyst regeneration tower 104. The catalyst regeneration tower canhave a plurality of regeneration zones or stages through which the spentcatalyst passes when undergoing regeneration. Regenerated catalyst 106is removed from the catalyst regeneration tower, and can be returned tothe reactor.

As illustrated in FIG. 1, a first effluent stream 108 and a secondeffluent stream 110 are removed from the top of the regeneration tower104. First effluent stream 108 is a gaseous stream that primarilycontains nitrogen, but can also contain oxygen and byproducts ofcombustion including, but not limited to, carbon dioxide. In oneexample, first effluent stream 108 can contain up to about 80% nitrogenand up to about 2% oxygen. First effluent stream 108 can also includebyproducts of combustion, including, but not limited to, carbon dioxide.The second effluent stream 110 is a gaseous stream that primarilycontains nitrogen, but can also contain oxygen and byproducts ofcombustion including, but not limited to, carbon dioxide. The first andsecond effluent streams can each have a temperature of from about 890°F. (477° C.) to about 1100° F. (593 ° C.).

The first effluent stream 108 is illustrated as being part of aregeneration gas loop intended to remove heat of combustion producedduring catalyst regeneration in regeneration tower 104. The firsteffluent stream 108 is passed through a conduit to a regeneration cooler112. Regeneration cooler 112 is a device utilized to remove heat fromfirst effluent stream 108 that is generated as the heat of combustion ofthe spent catalyst in the regeneration tower 104. A regeneration blower114 can be utilized to facilitate the flow of the first effluent stream108 from the regeneration tower 104 to the regeneration cooler 112. Theregeneration cooler is a heat exchanger, and is preferably an indirectheat exchanger having a hot side and a cold side as shown in FIG. 1A asregeneration cooler 112′. FIG. 1 shows a specific embodiment whereregeneration cooler 112 is a tube in shell type heat exchanger havingone or more tubes. When regeneration cooler 112 is a tube in shell heatexchanger, the first effluent stream 108 can be passed through the oneor more tubes of the heat exchanger to form a cooled effluent stream116. Cooled effluent stream can have a temperature of from about 700° F.(371° C.) to about 1000° F. (538° C.). Cooled effluent stream 116 canthen undergo other processing, in some examples can be passed back toone of the regeneration zones of the regeneration tower 104.

The CCR system illustrated in FIG. 1 includes a cooler blower 118.Cooler blower 118 receives atmospheric air, or ambient air from theoutdoors, and provides an atmospheric air stream 120 to the CCR system.The atmospheric air initially has a temperature equivalent to theoutdoor temperature, which can range between winter temperatures of downto about −10° F. (−23° C.) or below and summer temperatures of up toabout 100° F. (38° C.) or above, depending upon the location of thefacility in which the CCR process is being used.

Atmospheric air stream 120 can be divided into at least two air streams,including a first air stream 122 and a second air stream 124. First airstream 122 is provided to the regeneration cooler 112. When theregeneration cooler 112 is a tube in shell type heat exchanger, thefirst air stream 122 can be passed through the shell of the heatexchanger to act as a cooling stream for the first effluent stream 108.As first air stream 122 passes through the regeneration cooler 112, itabsorbs heat from the first the first effluent stream 108, and it exitsthe regeneration cooler 112 as heated first air stream 126. At least aportion of heated first air stream 126 can be separated and directedback into the CCR system as hot air stream 128. Any remaining portion ofheated first air stream 126 can be vented to the atmosphere. Asdescribed in further detail below, hot air stream 128 is preferablycombined with the second air stream 124 to form a blended cooling airstream 132. In this manner, the heat of combustion of the spent catalystthat is removed from the first effluent stream 108 in the regenerationcooler 112 can be utilized as a heat source to adjust the temperature ofthe blended cooling air stream 132.

As shown in FIG. 1, blended cooling air stream 132 is passed through aconduit to cooling zone cooler 130. Cooling zone cooler 130 is utilizedin the CCR system to provide a catalyst cooling stream 134 to a catalystcooling zone 136 of the regeneration tower 104. The catalyst coolingstream 134 is generated by a cooling gas loop in the CCR system.

As illustrated in FIG. 1, the cooling gas loop includes a first gasstream 138 that is removed from the cooling zone outlet 140 of theregeneration tower 104. First gas stream 138 contains air, and caninclude, for example, nitrogen, water, hydrochloride, chlorine andcombustion products. The temperature of first gas stream 138 can vary,depending upon the operating conditions of the regeneration tower 104.For example, first gas stream 138 can have a temperature of from about200° F. (93° C.) to about 1000° F. (538° C.). First gas stream 138 ispassed through a conduit to an air heater 142. Air heater 142 heats thefirst gas stream, for example to a temperature of about 1050° F. (566°C.), to form a heated first gas stream 144. The heated first gas stream144 can be divided into at least two gas streams, including aregeneration tower return stream 146 and a cooling loop stream 148. Theregeneration tower return stream 146 is passed through a conduit back tothe regeneration tower 104, and is provided to the drying zone 142 ofthe regeneration tower 104. The cooling loop stream 148 is passedthrough a conduit to the cooling zone cooler 130.

Cooling zone cooler 130 is a heat exchanger, and is preferably anindirect heat exchanger having a hot side and a cold side. In a specificembodiment as shown in FIG. 1A, for example, cooling zone cooler 130′can be a tube in shell type heat exchanger having one or more tubes thatact as the hot side of the heat exchanger. The cooling loop stream 148can be passed through the hot side of the cooling zone cooler 130 toform catalyst cooling stream 134. Blended cooling air stream 132 can bepassed through the cold side of the cooling zone cooler, which is theshell when cooling zone cooler 130 is a tube in shell type hatexchanger, to act as a cooling stream for catalyst cooling stream 134.

The temperature of blended air stream 132 is preferably greater than thedewpoint temperature of cooling loop stream 148. If the blended airstream has a temperature lower than the dewpoint temperature of thecooling loop stream 148, at least a portion of the cooling loop stream148 can condense as it passes through the cooling zone cooler 130. Overtime, condensation of the cooling loop stream 148 within the coolingzone cooler can cause corrosion. Without being bound by any particulartheory, it is believed that maintaining the cooling loop stream in agaseous state, and avoiding condensation thereof, will reduce or preventcorrosion within the cooling loop cooler. The dewpoint of the coolingloop stream 148 will vary depending upon its pressure. In someinstances, the cooling loop stream can have a pressure of about 35 psig.In such instances, the blended cooling air stream 132 can have atemperature of about 40° F. (4° C.) or greater. For example, blendedcooling air stream 132 can preferably have a temperature of from about40° F. (4° C.) to about 160° F. (71° C.), more preferably about 120° F.(49° C.). As the temperature of the blended cooling air stream 132increases, the efficiency of the heat exchange within the cooling zonecooler can be affected. Generally, as the differential between thetemperature of the blended cooling air stream 132 and the cooling loopstream 148 decreases, the efficiency of the cooling zone cooler 130 fora given volume decreases.

As it exits the cooling zone cooler 130, the catalyst cooling stream 134is in a gaseous state. The catalyst cooling stream 134 preferably has atemperature of from about 100° F. (38° C.) to about 300° F. (149° C.),more preferably about 160° F. (71° C.). If the temperature of thecatalyst cooling stream 134 is too high, its efficiency in the coolingzone inlet 136 of the regeneration tower is decreased. If thetemperature of the catalyst cooling stream 134 is too low, condensationcan occur within the catalyst cooling stream 134. Condensation can causecorrosion within the conduits of the process system.

FIG. 2 is a simplified flow diagram of one example of an air loop 200 ofa continuous catalyst regeneration process, such as the processillustrated in FIG. 1. As shown, regeneration cooler 202 receives afirst effluent stream 204 that has been removed from a regenerationtower (not shown). First effluent stream 204 is a gaseous stream thatprimarily contains nitrogen, but can also contain oxygen and products ofcombustion, and can have a temperature of from about 700° F. (371° C.)to about 1100° F. (593° C.). In one example, first effluent stream 204can contain primarily nitrogen, and can contain a small percentage ofoxygen. For example, first effluent stream 204 can contain up to about80% nitrogen and up to about 2% oxygen. The first effluent stream 204 ispassed through a conduit to the regeneration cooler 202. Theregeneration cooler is a heat exchanger, and is preferably an indirectheat exchanger having a hot side and a cold side as shown in FIG. 2A asregeneration cooler 202′. In a specific embodiment, the regenerationcooler can be, for example, a tube in shell type heat exchanger havingone or more tubes as shown in FIG. 2 as regeneration cooler 202. Whenregeneration cooler 202 is a tube in shell heat exchanger, the firsteffluent stream 204 can be passed through the one or more tubes of theheat exchanger to form a cooled effluent stream 206. Cooled effluentstream can have a temperature of from about 700° F. (371° C.) to about1000° F. (538° C.), but this temperature can vary depending upon theoperating conditions of the regeneration tower. Cooled effluent stream206 can then undergo other processing, in some examples can be passedback to one of the regeneration zones of the regeneration tower.

The air loop 200 illustrated in FIG. 2 includes a cooler blower 208.Cooler blower 208 receives atmospheric air, or ambient air from theoutdoors, and provides an atmospheric air stream 210 to the air loop200. The atmospheric air initially has a temperature equivalent to theoutdoor temperature, which can range between winter temperatures of downto about −10° F. (−23° C.) or below and summer temperatures of up toabout 100° F. (38° C.) or above, depending upon the location of thefacility in which the CCR process is being used.

Atmospheric air stream 210 is divided into a plurality of air streams,including a first air stream 212 and a second air stream 214. One ormore valves, such as, for example, illustrated valve 216, may be used todivide the atmospheric air stream 210. Valve 216 may also be used tocontrol and regulate the amount and flow rate of the second air stream214. First air stream 212 is provided to the regeneration cooler 202.When the regeneration cooler 202 is a tube in shell type heat exchanger,the first air stream 212 can be passed through the shell of the heatexchanger to act as a cooling stream for the first effluent stream 204.As first air stream 212 passes through the regeneration cooler 202, itabsorbs heat from the first the first effluent stream 204, and it exitsthe regeneration cooler 202 as heated first air stream 218. A portion ofheated first air stream 218 is separated and directed back into the CCRsystem as hot air stream 220. One or more valves, such as, for example,illustrated valve 222, may be used to separate and direct hot air stream220. Any remaining portion of heated first air stream 218 may be ventedto the atmosphere.

As illustrated in FIG. 2, hot air stream 220, or at least a portionthereof, can be combined with second air stream 214 from the coolingblower 208 to form a blended cooling air stream 224. In this manner, theheat of combustion of the spent catalyst that is removed from the firsteffluent stream 204 in the regeneration cooler 202 can be utilized as aheat source to adjust the temperature of the blended cooling air stream224. The amount and flow rate of the hot air stream 220 may becontrolled and regulated by passing the hot air stream 220 through oneor more valves. In the example illustrated in FIG. 2, the hot air streammay be passed through a valve 228. Hot air stream 220 and second airstream 214 can be combined or blended in any suitable ratio with respectto their amounts, volumes, or flow rates in order to obtain a blendedcooling air stream 224 having a desired temperature, volume or flowrate. For example, blended cooling air stream 224 can have a temperatureof about 40° F. (4° C.) or greater. Blended cooling air stream 224preferably has a temperature of from about 40° F. (4° C.) to about 160°F. (71° C.), more preferably about 120° F. (49° C.).

Blended cooling air stream 224 is passed through a conduit to coolingzone cooler 232. Cooling zone cooler 232 is a heat exchanger, and ispreferably an indirect heat exchanger such as, for example, a tube inshell type heat exchanger. Blended cooling air stream 224 can be passedthrough the shell of the cooling zone cooler 232 to act as a coolingstream for a cooling loop stream 234 to form a catalyst cooling stream236.

From the foregoing, it will be appreciated that although specificexamples have been described herein for purposes of illustration,various modifications may be made without deviating from the spirit orscope of this disclosure. It is therefore intended that the foregoingdetailed description be regarded as illustrative rather than limiting,and that it be understood that it is the following claims, including allequivalents, that are intended to particularly point out and distinctlyclaim the claimed subject matter.

What is claimed is:
 1. A continuous catalyst regeneration systemcomprising: a regeneration tower of the continuous catalyst regenerationsystem; a regeneration cooler in fluid communication with a firsteffluent stream that is removed from the regeneration tower wherein theregeneration cooler is an indirect heat exchanger; a cooler blower thatprovides a first air stream that is in fluid communication with theregeneration cooler to form a heated first air stream and a second airstream that is combined with the heated first air stream to form ablended cooling air stream; and a cooling zone cooler in fluidcommunication with the blended cooling air stream wherein the coolingzone cooler is an indirect heat exchanger.
 2. The method of claim 1,wherein the blended cooling air stream has a temperature of 40° F. (4°C.) or greater.
 3. The method of claim 1, wherein the blended coolingair stream has a temperature of from 40° F. (4° C.) to 160° F. (71° C.).4. The method of claim 1, wherein the cooling zone cooler is a tube inshell indirect heat exchanger.
 5. The method of claim 4, wherein theblended cooling air stream is in fluid communication with the shell ofthe indirect heat exchanger.
 6. The method of claim 1 wherein theregeneration cooler is a tube in shell indirect heat exchanger.
 7. Themethod of claim 6, wherein the first air stream is in fluidcommunication with the shell of the regeneration cooler indirect heatexchanger